The present invention relates generally to the field of generator control unit regulation and more particularly, to regulation of variable frequency generators.
In the field of variable frequency generators, it is often desirable to eliminate parasitic factors. Variable frequency generators and their generator control unit regulators have an associated open loop gain that can increase as a function of the speed of the variable frequency generator. Higher generator speeds can cause problems with closed loop stability resulting in poor transient response or instability when the open loop gain is uncontrolled.
Both the generator gain (output voltage/field current) and the generator control unit regulation loop gain can increase with speed if the regulator is supplied by an unregulated rectified permanent magnet generator, sometimes provided to the generator control unit by the generator.
It is known in the art to control the open loop gain of the generator and generator control unit by regulating the permanent magnet generator voltage using a pre-regulator to provide a constant field voltage supply over the speed range. One example can be seen in U.S. Pat. No. 6,909,262. The pre-regulators can include components such as transformers, inductors, etc. and can weigh as much as 2-3 pounds.
It is also known in the art to reduce the analog gain of the regulator as a function of the permanent magnet generator voltage before it is converted into a pulse-width modulated signal to drive a field control switch. This approach can result in narrow pulse-width modulation pulses driving the field control switch at higher generator speeds which can be susceptible to perturbation due to noise, which, in turn result in control loop inaccuracies and instability.
It is also known in the art to regulate a generator control circuit by employing various circuits to monitor voltage change rates and decrease the power to the generator when multiple conditions are satisfied. An example can be seen in U.S. Publication No. 2007/0159139 (FIG. 1). Still yet, it is known in the art to use a single pulse-width modulated signal, a switch, a regulator, and a fault condition detector to identify fault conditions on a vehicle generator. One example can be seen in U.S. Publication No. 2006/0061335 (FIG. 1). Such methods address excessive voltages on the generator but do not address regulating a consistent average voltage to the field winding as generator speeds increase.
As can be seen, there is a need for a lightweight and improved approach to regulating the open loop gain of a variable frequency generator.